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Are jets like the F86 still viable on the modern battlefield today?
Are jets like the F86 still viable on the modern battlefield today? Would it be better to build large numbers of older but cheaper jets such as the F86 in the thousands to swarm and overwhelm the enemy through sheer numbers rather than relying on more advanced but far more expensive jets that could only be build in limited numbers. As the saying goes quantity has a quality on its own.

You may want to consider that "overwhelm the enemy through numbers" is an amazingly bland way to say "get hundreds or thousands of highly trained soldiers killed for small gains". Even if you have no morals regarding the death of soldiers, pilots each take 18-24 months to train, and then you'll have to defend those losses to the government and the thousands of families who watched you hurl their sons into a meat grinder. Should we dispense with guns and just outfit the infantry with knives instead? They're much cheaper, and quantity has a quality of its own!

During the battle of Britain in 1940, the Luftwaffe had superior numbers of aircraft and much more experienced pilots. Both sides were able to produce new aircraft equally quickly. One of the major factors that helped Britain to survive to conflict was that most aircraft were shot down over British controlled territory which meant British pilots could be rescued and put back into the air, while German pilots were put into POW camps and so removed from the war.
Quantity alone doesn't cut it. A dozen F16's could have destroyed the Luftwaffe (or the RAF) without loss.

The most expensive part of an F86 swarm would be the pilots- and it would be unaffordable. Once you ditch the pilots, it makes little sense to have the individual elements of the swarm be as large as an F86.

I'm sure it's much much simpler and cheaper to train an early jet pilot like the F86 pilot compared to training a modern jet pilot such as the F16. After all our forefathers have done so during the 50s and 60s without issues

The "cost" involved has little to do with money/currency.

@WenHuiWong - The F16 is a much, much easier jet to fly then the F86. Modern jets are designed to allow the pilot to indicate what they want to achieve and the jet works out how to do it, which takes a huge amount of workload off the pilot, leaving them free(er) to worry about the fight.

@WenHuiWong a lot of the 50s and 60s pilots died due accidents coming from poorly understood aerodynamics and design https://en.wikipedia.org/wiki/Lockheed_F-104_Starfighter#Safety_record https://en.wikipedia.org/wiki/North_American_F-86_Sabre#Flying_characteristics. For your proposed human wave fighter you want modern a mass produced fly by wire system + modern aerodynamic design to get an easy to train for system.

The F86 sabre is good enough for thar task. I don't see why we can't continue to use the F86.


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Could air traffic control radars pick up a large stationary floating object?
Writing/formulating a story in which a large spaceship (≈1km/0.6 miles long, about a few hundred meters wide) spontaneously appears above land and (until authorities are noted of its presence) stays stationary where it appeared previously. Would nearby air traffic control radars be able to pick it up, and if so how would it appear on one?

While aviation radars might not pick it up, ground-based weather radar systems almost certainly will.

Radar may or may not pick it up, but an ancient technology (Mk 1 Eyeball) most certainly will. It's likely that the local police will know all about it within a minute or two of it's arrival.

shrimps might be able to detect it  ;-)

Radars will pick many airballons, or also large flock of birds. And more interesting: weather radar will see them (and they covers more larger area).

Summary
Your UFO will be detected, but:

Only by primary radars used by military. ATC centers usually use secondary radars, but they can also receive primary feeds in some cases. So ensure your ATC center has a primary radar source. In that case the size won't appear on ATC display, only a standard track, like for any aircraft.

ATC secondary radar detects only cooperative targets, i.e. targets with a system aboard (ATC transponder) replying to interrogations from the ground, or from other aircraft for collision avoidance.

Many tracking/detection systems in aviation work only with cooperative targets and don't see the other. Tracking sites like FR24 display only cooperative aircraft.

Military with their primary radars can see the actual size, but a target is visible on primary radars only if it reflects radar waves, it must be somehow conductive.

Stationary targets at low elevation over the horizon are difficult to extract from echos created by ground, buildings, etc. Most (primary) radars discard echos from stationary targets at low elevation.

Details follow. You can also create a chat room for additional discussion about details. This way anyone interested can freely provide information without having to meet the rules and format of a formal answer.
Primary vs. secondary radar
ATC radars are secondary surveillance radars (SSR). These radars actually interrogate a system, the ATC transponder, aboard the target. Without entering into details SSR work based with transponders of two compatible kinds: the older mode A/C and the modern mode S. If you need more information, we can provide it.

Source (adapted).
If the target isn't equipped with a transponder, or if the transponder is off, ATC SSR won't see anything. This is how MH370 disappeared from ATC radars soon after takeoff, while still in the coverage of land ATC centers. The transponder system became inoperative for some reason (unit switched off, or unit/antenna deteriorated).
However military have to detect uncooperative targets, and they use primary surveillance radars (PSR), the good old echo radar working by reflection on the target. In that case the radar station just sends a radio pulse and listen for any echo.

PSR stations may also be available at some ATC centers.
PSR stations use the Doppler shift to assess the target velocity. Targets stationary relatively to the radar station have no Doppler shift, the echo wave has the same frequency as the wave sent by the station. PSR stations may discard echos from stationary targets at low elevation, since most of them are just echos from buildings, trees, lakes, ground, towers, etc. So your stationary UFO might be discarded and not visible.
Not all materials are able to reflect waves of a certain frequency. Usually this is limited to conductive materials which can react to the wave as if the material was a transmitting antenna efficient for that frequency (technically it must be an electric dipole). If your UFO is made of plastic or stealth material, it will be transparent for waves and will reflect nothing significant.
SSR and PSR data can be mixed
In some countries (notoriously the US, as stated in other answers and comments), PSR and SSR stations are part of a network with a hub where all data from all stations are centralized, processed, correlated and redistributed to all ATC and military centers. In that case ATC operators will see an unidentified target detected by a PSR, without the exact altitude information (a PSR system is usually able to detect the direction, the velocity and the range).
PSR data may be discarded
Military are highly interested in uncooperative targets, ATC is not. It is possible ATC operators choose to not display PSR targets, only SSR targets. A reason is collision avoidance is based on altitude, and a target without an altitude cannot be managed, hence aircraft without a transponder able to indicate the aircraft altitude are usually not allowed to enter a crowded airspace controlled by ATC. There are ATC operators on this stack, they may provide additional details about that.
ATC operator may not see the unidentified target. If they see it, the size won't be indicated, a target being basically a line segment (track) with SSR data (transponder id, altitude, speed, vertical speed) displayed as a label close to the track. Stationary targets may be indicated using a specific symbol. As the operator who assigns the transponder id ("squawk code" in mode A/C) can associate this id with the aircraft flight plan and the flight number, often this flight number replaces the transponder id on ATC displays.

STARS ATC symbol for an aircraft, source.
Whatever, if military detect an unidentified target, they will inform related civil ATC units. Actually it's possible a military controller will be present in the civil ATC unit, working with a civil controller to coordinate military and civil traffics.
Questionable targets in the US are managed according to §5.3.2 of FAA Order JO 7110.65AA.
Weather radar
Many civil aircraft have a weather radar onboard, they may detect the uncooperative target, as these radars work by reflection on water droplets (rain in the cloud and below them).
These radars show somehow the actual horizontal shape of the target by reflecting on droplets at any distance. However a solid target may be impermeable to waves, echos will be limited to the envelope portion facing the aircraft, the target will appear as a silhouette.
Weather radar pulses are sent close to the horizon, they don't illuminate targets in the ground direction. The weather radar of an aircraft flying at a high altitude won't see a UFO hovering close to the ground .
Collision avoidance system
Many aircraft (incl. all commercial aircraft) have a collision avoidance system aboard. This system works like a SSR station, it interrogates the transponder of other aircraft in the vicinity, to know their position and altitude. Such systems won't see any target not equipped with a transponder.

Thank you for addressing Doppler!

An air traffic control unit using only a single secondary surveillance radar, may still "detect" the UFO if it blocks the radar signal. When the UFO is between the radar and the aircraft, the aircraft is no longer visible. The sudden lack of aircraft in a sector would certainly be noticed. A 1km long object could take quite a chunk out of the radar coverage if it is not too far away from the radar. However, many ATC systems use multiple radars and multi sensor data fusion, so as long as those missing aircraft are seen by other radars, the air traffic controllers will not notice anything.

"If your UFO is made of plastic with organic creatures inside, it will be transparent for waves and will reflect nothing." This and other definitive statements about being unable to detect via radar are stated too strongly. Yes, conductive (metallic) materials are dramatically better at reflecting radar, but organic materials do so too, just much less. How radar observable something will be is greatly dependent on many factors. As to organic material showing up on radar, a search for "flock of birds on radar" shows many examples.

@DeltaLima Yeah, I was going to say I suspect such an object would be seen by ATC as their radar set detecting an error. It probably depends on the specific software package, but that's likely to show up as bad data that might indicate damage to the set.

@mins That really depends on how you define "organic matter". I'm not aware of any organism above a virus that doesn't have water as a substantial portion of its mass. Thus, I'd assume that "organic creatures" (and their support) are highly likely to include water (or at least some other substance that's similarly reflective). That doesn't mean that the UFO couldn't have been intentionally constructed to not show up on radar, have shields, or cloaking, etc., but that's not part of the question.

@Makyen, that's a good point, thanks.

Such a spaceship would be very easily "painted" by any radar system in use today—unless it was designed specifically with radar stealth in mind, and even then its immense size would make it very difficult to stealth-ify. However, as @RetiredATC mentions, if it were stationary that may well prevent it from appearing on radar scopes because of the Moving Target Indication feature.
In the usa, considering only the software used by Terminal (low-altitude) controllers that I am familiar with, there are two possibilities: the ship could be depicted as a primary-only radar target or as an area of presumed precipitation. (It is not uncommon for the software to interpret larger-than-aircraft targets, such as a windmill farm or a large flock of geese, as an area of precipitation.)
A primary-only target is shown as a green diamond shape within a blue circle. Coincidentally the blue circle is approximately 0.6 NM wide on the scope, although the exact size does vary a little based on the range setting.
Precipitation is shown in 0.25 NM-by-0.25 NM square chunks. The ship would probably be "light" precipitation, which is a light blue color, of perhaps 3x1 or 3x2 chunks.

Does the Moving Target Indication filter out hovering helicopters? If a helicopter stops squawking and starts hovering, does it become "invisible" to ATC?

Haven't seen that before @vsz, that I've noticed anyway. If the target is squawking it will stay on the scope of course, as you alluded to. And if it was squawking but it stops squawking the system is almost always able to still track it and still associate it with the existing flight data. If it was never squawking in the first place then the MTI likely would end up excluding it, at least after a little while.

@vsz and if it stops squawking while being tracked it'd most likely also be flagged as there is potentially a serious problem with the aircraft (electrical failure, crash, etc.).

If the object reflects at least as much radiation as a Cessna 150, traffic control radar can see it with a "skin paint".  Unfortunately, if they're in normal operating mode, they look almost exclusively for transponder squawks, and even a huge reflection might be filtered out by the radar's computers.
Weather radar would be even worse, as it looks primarily for Doppler effect indicating motion toward or away from the antenna.
Military radar (especially threat detection sites) would easily pick up anything even as large as a good sized drone, however, and is far less likely to be dependent on transponder identification to put a blip on the operator's screen.

Really? I hear ATC give traffic alerts with altitude unknown pretty frequently. I guess those could be people with just a mode A transponder, but I'd think that's probably even less common than no transponder at all.

It depends on the altitude of the object and the distance from the radar antenna. The further away from the antenna and the lower the altitude the harder it is for the radar to detect. Additionally, if the radar did receive a return from the object, it would likely not be shown on the controller's display. Air traffic computers try to filter out objects that are not moving because it's looking for airplanes, which move (known as moving target indicator in some installations).

@Chris (and @ZI): in the USA, ATC radars are almost invariably combined primary-and-secondary units so they will detect both transponder-equipped and non-transponder-equipped targets. Only in very rare cases are secondary-only radars used. (Of course ADS-B-only receiving sites have become quite common but they are mostly used to supplement traditional radar.) In other countries secondary-only radar may be much more common.

What is true in the USA is that controllers whose airspace consists is entirely Class A are allowed to disable the display of primary-only targets on their scopes, because the assumption is that anyone who may be a factor for Class A traffic is transponder-equipped.

I'm skeptical of the assertion that ground-based weather radars will filter out returns that aren't moving towards or away from the antenna.  If nothing else, that would lead to the forecasters completely ignoring weather systems that are moving perpendicularly to their line of sight.

@MichaelSeifert Weather radar isn't looking for objects; it's looking for precipitation, and detects it almost exclusively by Doppler.  That's how (for instance) weather radar can detect the "hook cloud" or "cat's paw" clouds associated with tornado formation: it's full of raindrops, and their motion reveals the rotation of the cloud.

@ZeissIkon: Right, but the raindrops reflect radar regardless of their motion, and the stations collect that information too. If you go to the NWS radar map and select a local radar map, you can see both the reflectivity data and the velocity data in separate layers. The reflectivity layer tells you how much of the radar signal bounced back (i.e., how many raindrops/alien spacecraft are present.)  The velocity layer tells you how fast it's moving. A stationary spacecraft would show up as a shaded area on the first map and a gray area on the second map.

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Issue with Telegram Dates
Flight 1234 was originally scheduled in the daily flight plan for 02.12.24 (Planned date) but was rescheduled to 04.12.24 due to weather conditions.
In the specialized flight operations software:

The Planned date remains as 02.12.24.
The Estimated and Actual dates are updated to 04.12.24.

On 04.12.24, LDM and other telegrams referencing 04.12.24 are received. However, the software displays the following event:
"Flight 1234 for 04.12.24 was not found in the daily flight plan."
As a result, the telegrams are not linked to the flight.
Could this issue be caused by:

An error in the software's algorithm, which seems to link telegrams to the Planned (scheduled) date instead of the Actual date?
A formatting issue in the telegrams, as IATA (or other) regulations specify using the Planned (scheduled) date?

If the latter, could you please clarify which specific documents state that telegrams must always use the Planned (scheduled) date rather than the Actual date?
Thank you for your assistance!

This information should be available in the IATA Airport Handling Manual (AHM 583 message). Do you have access to this manual?

@mins hi and ty for reply! Unfortunately, I do not have access to the IATA AHM. Too expensive for me ):

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What is the FAA definition of solo flight?
If I'm a student pilot (for commercial), and I flew for pleasure with friends one night, do I log those hours as solo? Does solo mean, only pilot in the aircraft? Or does it literally mean only person?

If you only have a Student pilot license, you broke the law & you might want to avoid logging that flight altogether! Assuming that isn't the case, and you do have a Private license, why not log the flight as PIC?

I'm a commercial student pilot. So yes, I have my private.

Cool. So log it as PIC.

To be more correct: you aren't a student pilot, you're a private pilot who's working towards a commercial certificate. Once you get your private certificate (in any category) you're never considered to be a "student pilot" again.

According to FAA, it means that the pilot should be the only person in the aircraft. According to 14 CFR § 61.51 - Pilot logbooks,

(d) Logging of solo flight time. Except for a student pilot performing the duties of pilot in command of an airship requiring more than one pilot flight crewmember, a pilot may log as solo flight time only that flight time when the pilot is the sole occupant of the aircraft.

14 CFR § 61.8761.87 - Solo requirements for student pilots also says pretty much the same thing:

(a) General. A student pilot may not operate an aircraft in solo flight unless that student has met the requirements of this section. The term “solo flight” as used in this subpart means that flight time during which a student pilot is the sole occupant of the aircraft or that flight time during which the student performs the duties of a pilot in command of a gas balloon or an airship requiring more than one pilot flight crewmember.

I am assuming you have a Private Pilot's certification?
(SEL or MEL etc. does not matter as long as you are type rated and certified to fly the airplane you going to go fly in with your friends)
If so, technically this flight of yours goes in your log book as just another regular flight. Can you count hours towards another certification (towards Commercial)? Yes, since you are still PIC. What you cannot do is be compensated for that flight. Pro-rate based fuel sharing is acceptable.

Although everything in this answer is completely true, it doesn't address the actual question.

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What is a public airport?
I know that ALL airports that have received federal funds are considered to be open to the public, however does that mean that every "public" airport was federally funded?

You can check out this info from the FAA
And the official FAA definition:

Public use airport is an airport available for use by the general
  public without a requirement for prior approval of the airport owner
  or operator.

It should be noted that 4 airports in the US are considered "High Density" and have special rules about operations during certain times which require approval for use (arrival/departure) despite being public.

§93.125   Arrival or departure reservation.
Except between 12 Midnight and 6 a.m. local time, no person may
  operate an aircraft to or from an airport designated as a high density
  traffic airport unless he has received, for that operation, an arrival
  or departure reservation from ATC.

In answer to the question as its now worded,
No, there are public airports that are not federally funded. The airport I currently fly out of KDYL is owned and operated by the local government (Bucks County) and they are responsible for most things that go on there. I am not sure if they have received Federal funding in the past but I will ask around.
There is also such thing as "Privately Owned/Publicly Used" (elsewhere called POPS) airports like Trenton Robbonsville N87. These airports are owned privately, run privately, and generate their own income however you don't need to prior approval to land there and are open to general public use.

Are USAF bases, I assume federally funded, open for public use?

@mins Im not sure across the board, I know at least one locally, KSWF, has a large Air National Gard base on site and is open for GA and Commercial traffic. Im not sure Id try landing at KXTA though....

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Can I log this as total time?
I am a CFII who has a commercial multi-engine certificate. My friend was building time in a BE-58 Baron (multi-engine) for his MEI. He asked me to tag along (right seat)since he was going to file IFR and fly in some IMC.
Since he is logging the PIC, and all I did was tune in the freqs and programmed the avionics, can I log this as total time?
Also since we flew in IMC can I log the “Actual Inst” time?


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What is the difference between COM and Auxilary COM signals?
when the aircraft navigation system is tuned to VHF COM frequency (118-137.990MHz) then COM receiver will able to receive two types of signals one is COM signal and the other is AUX COM signal what is the difference between them ?

Is this for a specific aircraft?

Can you explain exactly what an "AUX COM signal" is? Do you have a link or a picture? "AUX audio" often means connecting a Bluetooth device for music or phone calls, but I don't know if that's what you mean here.

Info on the particular aircraft and com stack would be helpful in answering this question. Aux generally stands for "auxiliary" which by definition means "providing supplementary or additional help and support.". What it means in this context could vary. It could, for example, be an input for an auxiliary antenna.

That frequency range is not for navigation equipment at all, so I would speculate that it isn't related to the navigation system.
They don't receive two types of signals; they do the exact same thing, but the reason someone may want two radios is to make things easier during flight.
What I think you are seeing is your primary communications radio system, and then a switch for an additional, optional "Com 2" unit that may or may not be installed in the aircraft.
Let's say you are talking to air traffic control, and you want to listen to an automated weather station without having to leave the ATC frequency; most systems provide you with an option to listen to both Com 1 and Com 2 at the same time, while allowing you to transmit on only one of them.  That way, you could monitor and talk on ATC's frequency on Com 1 while getting a weather update on Com 2.
Another advantage is that you can transition between frequencies faster by simply changing from Com 1 to Com 2 (ie. "AUX COM") after having already set the frequency you want to switch to in the other Com.
Yet another advantage is that one com will act as a backup to the other if either one stops working for some reason.

This may be in reference to the precision of band devision used in radio communications. Most older aircraft radios are only tunable to the 0.00MHz frequencies, while some newer ones may be sensitive enough to tune into 0.000MHz bands. Generally when tuned to say 120.00 on an older radio you will be able to pick up 120.00 as well as 120.005 while some planes are now capable of discreetly tuning to these frequencies. Thus AUX COM signals are those that live in the .000 bands


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Does MCP Altitude change in the B757/B767 when ALT HOLD is pushed?
I have a question, resulting of a discussion in a different forum: When flying the B757 or B767 and the ALT HOLD button is pushed, will that also change the MCP Altitude to the current altitude, at which the aircraft was, when the button was pushed?
Example: I am flying at FL300, I set my MCP Altitude to 15000 feet. At 18000 feet I push ALT HOLD. Will that change MCP Altitude from 15000 to 18000 feet? I know that some aircraft like the ERJ and the B717 and the B737 do that. I have however never flown a B757 or B767 in real life and I have heard several opinions regarding it.
Also, is this a default setting or this there maybe an operator option to have such a feature fitted? Has there been a refit, where this has been added? Unfortunately the only B757 pilot I know last flew one six years ago, so I don't know.
Thanks in advance for your answer.
Cheers,
Ben

No, in a 737 pushing ALT HOLD won't change the MCP altitude. The aircraft will level off at the altitude where you pushed it, but the MCP altitude won't match that -- which is still a normal place to be, holding one altitude while what's in the MCP window reflects what you're cleared to (perhaps at pilot discretion).
Can't speak to the other Boeings you mentioned, but the same logic would apply.

Thanks for the clarification! Maybe I just don't remember well. It has been a long time since I last was in 737 and my TR for it expired. Current operator only maintains ERJ and Airbus.


text:
What are the "spur" devices on this U2 pilot's boots?
From this video on YouTube:

What are those devices and what is their purpose?

Do we need a tag for spacesuit, uniform, flying-clothes or perhaps "safety-spurs"   ?

"Pilot personal equipment"?

These are part of the foot restraint system fitted to the seats used in the SR-71, later U-2 and some Space Shuttles. (They're all derived from the same basic design).
The spurs engage in two ball nipples that protrude from the lower part of the seat. The nipples are connected via cables to reels beneath the rear of the seat which pull the pilots feet in during the ejection sequence.
The seat separation sequence severs these cables (amongst other things) allowing the seat to drop away.
You can see the nipples on the lower part of this Space Shuttle seat:

Source:The Ejection Site

I figured they were related to ejection, but I also wondered about use of rudder pedals. The idea of cables makes a lot of sense.

Hmm... I'm now curious under what circumstances one could eject from the Space Shuttle. That seems like it would end very badly in almost any phase of flight, except maybe the last minute or so before landing.

After reading here, it looks like the pilot of the first Shuttle mission shared my concerns and the ejection seats were removed entirely after the first few flights. Apparently they were only ever installed on Columbia and Enterprise (the unpowered test craft) in the first place.

@reirab, I understood that the main reason they were not installed was the double-decker design. The test missions only had anybody on the upper deck.

@reirab, in the first fatal accident, ejection seats would have actually likely helped—the break-up forces did not exceed 20g and the cabin held together and descended at subsonic speed, so ejection during the descent would have been within envelope. The envelope would still be inferior to launch escape system like capsule spaceships have and it's not clear it would be sufficient in case of on-ramp accident (like the LES did on Soyuz T-10-1.

@JanHudec Yeah, that's a good point about Challenger, actually, since the SRBs separated from the stack when the external tank began disintegrating. Normally, I would think that ejecting during launch would lead to a very unpleasant encounter with the exhaust plumes from the SRBs (and apparently the pilot of STS-1 shared that concern.)

@reirab, yes, but it would probably be possible to design the abort sequence to detach them, or the orbiter, first. The detaching mechanism is there for when they burn out already.

Wayne Hale wrote about the space shuttle ejection seats in his blog when he was with NASA: https://blogs.nasa.gov/waynehalesblog/2008/11/12/post_1226523744082/

Those were attachments for the ejection seats leg restraints to be used when bailing out of the aircraft in an emergency.


text:
Why is the gear handle shaped the way it is?
In the aircraft cockpits I've seen, the gear handles all seem to have the same general shape (they look like a little wheel). Is there a reason for this beyond simply making it absolutely obvious that it's the gear handle?

It's required by law, at least in the US. 14 CFR 23.781, Cockpit control knob shape specifies these shapes for the flap and gear controls on smaller aircraft:

For larger (transport category) aircraft, 25.781 specifies the same thing:

As for why those shapes are specified, it's for at least two reasons:

The shape resembles the thing it controls, so it's an obvious memory aid
The controls are all shaped differently, therefore you can distinguish them by touch alone, without needing to look at them

As others have noted, there have been accidents in the past caused by pilots using the wrong controls, and this is one reason why the FAA decided to do something to standardize them. Parts 23 and 25 also state where the controls should be placed, for the same reason.
The FAA's Airplane Handbook says:

There have been many cases of the pilot mistakenly grasping the wrong
  handle and retracting the landing gear, instead of the flaps, due to
  improper division of attention while the airplane was moving.

They recommend - and I was taught - leaving the flaps alone after landing until clear of the runway (unless you have a good reason for retracting them earlier, like a short-field landing), then check and retract them with the statement "flaps identified and retracted". "Identified" in this case simply means that you're sure you have the right control in your hand. Some instructors even avoid touch-and-goes in complex aircraft (i.e. with retractable gear) because they feel the risk of retracting the gear rather than the flaps during the maneuver is too high; they stop and go instead, even if that means taxiing back for takeoff.

i think its important to add that before this regulation went into effect, there were many accidents when the pilot tried to put the gear down or up and used the flap control instead, because the two controls similar in shape and co-located. for example, here's the gear and flap control handles on a DC-3. I can't tell which is which. http://www.maam.org/airshow/images/r4d_cockpit_17.jpg

@rbp Good idea, I've expanded my answer

Excellent answer, thank you. I wish the images were a bit better, but they're great none-the-less.

@Steve Well, that's the image quality that the FAA has on their website. Good enough for government work, I suppose :-)

Specifically, it was due to gear retraction of the B-17 and the solution proposed by Alphonse Chapanis https://en.wikipedia.org/wiki/Alphonse_Chapanis

For that natter, why retract the flaps at all after landing?  You're just going to need to extend them again the next time you take off, anyways...

@Sean That depends on the aircraft. In a C172, for example, you don't use flaps in a normal takeoff so during a touch and go you retract them.

making it absolutely obvious that it's the gear handle

This is the very reason. Cockpit ergonomics are not only to make things easy to use but easy to tell apart. Here is an incident in a smaller plane as a result of flap handle/gear handle confusion. Here is an NTSB report on the same issue with Beech Bonanza
If memory serves this also happened on a bigger plane once (im trying to find the accident report).
There has also been a push to make cockpits at least similar across the board to avoid issues. The best example of this issue has been the difference between American and Russian made attitude indicators which offer the visual appearance of being reversed of each other. You can read about that here.
As for why there is specifically a little wheel on the lever you can check out this discussion over on airliners.net about that very topic.

Isn't the best example the fact that Cessnas and Pipers have the throttle and carb heat levers opposite ways?


text:
What kind of helmet is in this A-10 video?
Here is a screen capture from a YouTube video. The aircraft is an A-10.

What kind of helmet is that and where can I learn more about it?
Additionally, does the weight of the helmet and it's apparently awkward center of gravity cause issues during high-G maneuvers?

AFAIK, the A-10 does not pull high-g maneuvers, relatively speaking. (Relative to air superiority fighters.) This means it can afford heavier helmets with more features.

The pilot's helmet in the photo is a standard Gentex HGU-55/P fitted with a Thales Aerospace Scorpion Helmet Mounted Cueing System.  Information on the SHMCS is available on the corporate website
http://www.thalesvisionix.com/overview/
As to weight, the display, cableing, and visor add several ounces of extra weight to the helmet.  It's a little heavier and slightly bulkier than a standard visor on a helmet but not by much.  Aircrews have been flying with HMDs now for about ten or so years without any major impediments to their flying abilities.
There has been a weight issue associated with the F-35 HMD and the aircraft's ejection seat which could cause a fatal whiplash injury during ejection with smaller pilots.  This is being remedied with changes to the seat's pneumatic catapult system, drogue chute deployment timing, both controlled by a selector switch prior to flight, and a newer, lighter version of the helmet under development.

I expected to see "more" under the dark visor. It looks like most of that space is to accommodate night vision goggles. Is the visor's purpose mainly to increase the visibility of the in-helmet HUD, with the secondary purpose of looking bad-ass?

No, it's just a standard sun visor

To add, the F-35's helmet weight issue only affects pilots under 135 lbs (elevated risk of whiplash). This currently affects only one (male) pilot in the pool. The lighter version will have a detachable visor to save weight (among other measures).


text:
What does the statement painted on this P-51 mean?
In this video, there is a shot of the side of a P-51 Mustang.

The side of the plane is painted with:

SERVICE THIS AIRPLANE WITH GRADE 100/150 FUEL. IF NOT AVAILABLE T.O. 06-5-1 WILL BE CONSULTED FOR EMERGENCY ACTION
  SUITABLE FOR AROMATIC FUEL

What does this mean?

They are instructions for a compatible fuel substitute for 100/150 octane fuel per Technical Order 06-5-1 if AvGas is unavailable to the service crews in an emergency.

In my opinion, it's a reminder that 1) fuel should be 100-150 octane, and 2) when not available, a gasoline rich in aromatic hydrocarbons (i.e. high-octane) could be used in emergencies, following the document T.O. 06-5-1.


text:
What IFR clearances may a pilot obtain from ATC directly without a pre-filed flight plan with FSS?
I have known two types IFR clearance that a pilot may request with flight plan filing.

Pop-up clearance: A pilot on VFR requests an IFR clearance to destination airport. ATC grants a clearance on a work-load permit basis.
IFR Climb to VFR-on-top: A pilot may obtain this type of clearance from ground clearance delivery and the clearance limit is usually a nearby Nav aid.

The unlikely clearance without pre-filed plan is,

Airport-to-airport: Ask ground clearance delivery for an IFR clearance to another airport.

What other types of IFR clearance else may I request ATC directly? We know that the flight plan checked-in time needs to 30 min prior to its start time.
Another example is

"IFR-descent-to-VFR-under-bottom": Is it possible to request an IFR descent through a cloud layer, say 8000 to 5000 through a layer 6000~7000? Is it just one special case of "pop-up clearance", or due to the descent nature, ATC won't grant it?

Are there any concrete regulations or general conventions that a pilot may follow?

Any IFR clearance that is requested from ATC without having pre-filed is, by definition, a pop-up.

Also, if you're flying a TEC route from airport to airport, you don't need to file before calling for clearance.

The theoretical answer to your question is that you can always get an IFR clearance directly from ATC over the radio, and filing a flight plan in advance isn't required (but it is strongly advised to avoid delays).
In reality, however, you should file in advance if at all possible. This is from the AIM 5-1-8 (my emphasis):

Instrument flight plans may be submitted to the nearest FSS or ATCT
  either in person or by telephone (or by radio if no other means are
  available). Pilots should file IFR flight plans at least 30 minutes
  prior to estimated time of departure to preclude possible delay in
  receiving a departure clearance from ATC.

The IFR flight plan system is there for good reasons: it helps ATC manage busy airspace and it avoids the need for lengthy radio discussions. If you don't file a flight plan in advance then you'll probably annoy ATC and you may be delayed because they can't take your request directly.
Pop-up clearances by definition don't have a full flight plan filed in advance, but they do have an abbreviated IFR flight plan:

An authorization by ATC requiring pilots to submit only that
  information needed for the purpose of ATC. It includes only a small
  portion of the usual IFR flight plan information. In certain
  instances, this may be only aircraft identification, location, and
  pilot request. Other information may be requested if needed by ATC for
  separation/control purposes. It is frequently used by aircraft which
  are airborne and desire an instrument approach or by aircraft which
  are on the ground and desire a climb to VFR-on-top.

Weather isn't predictable and a VFR flight may have to become IFR for safety reasons, so there needs to be some flexibility for aircraft that are actually in the air. A pop-up clearance is just a different, simpler way of requesting an IFR clearance; once you have it, you're IFR and operating in exactly the same way that you would if you had filed in advance.
Descending to VFR conditions is an interesting idea but ATC can't clear you to descend below the minimum IFR altitude for the area. You could request the lowest altitude ATC can give you, then cancel IFR if you break out. But descending without a specific altitude restriction seems very risky: the temptation would be to keep going lower to "have a look", and that could end up as a CFIT incident.
Finally, at least in my experience the 30-minute 'rule' is really a guideline to avoid delays. I've never had an issue filing IFR and departing 15 minutes later, but then I'm usually flying between class C or D airports and the airspace isn't particularly busy. A class B airport is probably a different story.

What about tower enroute control (TEC)? Supposedly you can pop-up and request TEC- ref https://www.flyingmag.com/technique/tip-week/tower-en-route-control


text:
Can a CFI endorse a BFR flight review through real-time video including the flight portion?
Context: To minimize the heath risk during pandemic, many CFIs, especially senior ones, are not comfortable to conduct instructional flights with students in a narrow cabin. In the meantime, many pilots are due soon for flight reviews (BFR), but still within the 24 calendar month valid period.
For the ground portion of the flight review, a remote video call should make no difference with respect to regulation compliance. So the remaining of the question is for the flight portion,
Is it regulation-compliant to let a CFI to endorse me while the CFI is on the ground while I am going solo for the flight? There will be real-time videos, which cover the flight instrument panel, my maneuvers and cockpit outside views, broadcasting to my CFI in real-time, as well as recorded for post-flight verification. The CFI will be able to communicate to me in real-time through a hand-held radio, and will watch my takeoffs and landings near the runway, just like what happens on a first solo.

See SFAR 118, 118-1 and 118-2 for special COVID-related relief of many currency requirements. That should give you enough additional time to find a CFI willing to do a Flight Review in person. Many schools have reopened, and many never closed, so it shouldn’t be difficult.

How do you plan on setting up this real time video? A regular cellphone connection isn't going to be enough, and that much data is going to be expensive.

Although, I can not find anything that explicitly prohibits a pilot who meets currency requirements from receiving a Flight Review this way, 91.109 strongly implies that the CFI must be able to manipulate the controls of the aircraft. It may be easier to just accomplish a WINGS phase. It seems to have fewer concrete stipulations.

@DJClayworth, I did saw some real-time broadcasting YouTubers and I guess there would be some good-signal area. I'm also on an unlimited data plan. Nonetheless, I am researching it is legally compliant before starting to search for these zones.

@StephenS These are great pointers that give me more room of time.

@DeanF. I think the CFI should able act as a PIC when conducting flight reviews.

It seems to me that your question is simply "can an instructor provide flight training from the ground?", whether it's for a flight review or something else. As far as I can tell, the instructor must be in the aircraft. All emphasis below is mine.
61.1:

Flight training means that training, other than ground training,
received from an authorized instructor in flight in an aircraft.

61.195(g)(1):

(1) A flight instructor must perform all training from in [sic] an
aircraft that complies with the requirements of §91.109 of this
chapter.

The Williams interpretation (2018) talks about instructing from the rear seat (see this somewhat related question) and states that the regulations require the instructor to be seated in a pilot station per 61.195:

Section 61.195 prescribes limitations and qualifications for flight
instructors. As evident from the heading in § 61.195(g), § 61.195(g)
prescribes limitations on the flight instructor's position in an
aircraft and required pilot stations for flight training.
[...]
The regulation would not require two pilot stations for a training flight unless the flight instructor were required to provide flight
training from the one of the pilot stations.

That last statement seems very clear. In any case, the idea of providing flight instruction from the ground doesn't seem realistic, in my opinion. Even with great cameras, will the instructor be able to see your knuckles are white on the yoke from poor trimming technique? How would you do exercises under the hood (if needed)? There are just too many things that would be difficult to do and/or difficult to assess.


text:
What are effective ways to spot the aircraft ATC specified?
When ATC instructs me something like "There is a Skyhawk on your 2 clock, 7 miles, 6500". I am not able to spot the target at least half of the time after several ATC reports its position until ATC says "not a factor" or gives me a new heading or altitude assignment.
I am wondering if there is any effective ways to get the aircraft spotting skill? Or knows my limit that it is nearly impossible to see it if it beyond a certain range and give up searching. When entering busy airspaces, the aircraft looking is taking a large portion of cockpit time.

"When entering busy airspaces, the aircraft looking is taking a large portion of cockpit time." Looking out should take a large portion of your time wherever you are!

Don't spend too much time trying to find a small aircraft 7 miles away, you could miss something much closer ATC doesn't see. Look in the general direction for a second or two, then pick up your outside scan again.

Also remember that when ATC says 2 o'clock, they mean relative to your track, not your heading. Usually is difficult to spot something small like an aircraft from 7 miles. You are trying to see something 40 feet wide from a distance of 35,000-ish feet away, plus it's moving and probably white. Don't get discouraged, just keep an eye out and report if you see it, don't see it, or more importantly saw it but lost it.

Also helps to know where to look with respect to the horizon: right at it, just above, just below, for aircraft height with respect to your aircraft.
In my airplane, I just had a GPS moving map unit installed that displays ADSB-Out info from other airplanes. The couple of times I have flown with it, it was way easier having a clear heading to look towards, and then scanning back and forth and up and down a little.
Might be USA only requirement, but I don't anticipate flying much elsewhere.  Canada and Bahamas for vacations would be about the extent of my foreign travel. Bermuda - oneway!

(Daytime flying only. Peripheral and night vision is different and I have zero practice of night flying.)
The highest resolution part of the eye is the fovea, and it's surprisingly narrow. If a small, slow-moving object is outside this area it probably won't be seen. If you scan from say 20 degrees left of an object to 20 degrees right of it you will also miss, because the eye tends to jump in steps and we only see a small fraction of what is actually in front of us.
So I was always told to gaze steadily, in ten degree steps, for a few seconds at each area. A grid of search areas both above and below the horizon should be checked. You'll only recognise an object when your fovea is virtually on it.

Only look for a second or two at each are because any longer and the vision "bleaches" and you are even less likely to recognise anything in that region; just keep moving on to the next.
The narrow 10 degree steps are that size because that's the region
of acceptably sharp vision. (I suspect it differs between individuals)
This was what I was taught for general lookout, though I suppose it should apply to a specific search area given by ATC too.

Apparently these tips were all derived from RAF training for this sort of thing, but I don't have any notes on that.  In any case I suspect it's more practice than bookwork anyway.
One of my gliding instructors liked the spotting game. One point for every aircraft I spot before him. He had one dodgy eye and of course still won by an appalling margin... (I've also heard some play this game for beers, though frankly none of my instructors would ever be able to drive home.)

A lot of it is about disciplined scanning:

Don't move your head, move your eyes
Scan up and down, left to right, like a lawnmower; be methodical
a difference of 1000 feet at 10 miles is about 1-degree, which is the angular diameter of the moon which is the width of 1 finger held at arm's length; so for example, if it is at 6500 7 miles away and you are at 4500, then it is about 3 moons/fingers above your horizon

If you missing stuff, the most likely reason is that you are looking around randomly, instead of lawnmower scanning

If your windscreen is liberally coated in bug spatter, amending the procedure to include moving your head (like an owl) can be effective in tunning out the spatter.

Even if you never spot the plane being pointed out to you, the act of scanning to find the traffic will improve your safety factor. If the plane you are looking for does become a factor, you will see it sooner if you are looking for it than if you are not.
I guess the point of my answer is that you should not stop trying to spot planes that are called out to you, even if you aren't very good at spotting them because it still makes everyone more safe.


text:
Do all Class B and Class C towers operate 24/7?
For Class B airports, I think the answer is realistically yes, due to traffic flows. How about Class C airports? Are there any legal requirements that it has to operate in 24/7, or is a convention?

I believe KXNA is an example.

No, many class C airports close, for example KGRB is attended 0500-2200 and closed at other times, during which the airspace turns into class E or G (can't remember).

Here is another example - KMRY.

The short answer is no. It's easy to find examples of class C towers that aren't 24/7, by checking in the Chart Supplement. Two examples are KXNA (as mentioned in the comments) which operates 1130-0500Z and KHSV, which operates 1200-0600Z. Note that the airspace changes when the tower is closed: KXNA becomes class G, and KHSV becomes class E.
As for class B, I would also assume that they're 24/7. I checked a few (KATL, KBOS, KSEA) in the Chart Supplement and they are indeed 24/7 but I don't feel like checking them all :-)

KNKX although not public use is class B and is not continuously manned.

@RonBeyer That's an interesting example. The Chart Supplement says it's E, not B, but the TAC certainly makes it look like B.

Wikipedia lists it under class B, that's where I got it from.


text:
In case of transponder failure, can I use my ADS-B out (Stratus II) serve as a back-up?
When the transponder fails, would ATC pickup my altitude response from my Stratus or any other ADS-B out instead? Is it legal to do so?

Which airspace? Generally the answer is no.

Do you have a link to the specs of the Stratus II, I can't find it.

The Stratus does not broadcast. It recieves only. So that is no help.
If you had a stand alone UAT ADS-B transmitter. It might continue to broadcast your altitude if your transponder failed. The UAT requires an altitude input and it must be from the same source that your transponder gets it. Sometimes that gets wired directly from a 2nd output of your altitude encoder (bypassing the transponder which gets it from the 1st output) in which case it would continue to broadcast altitude. Sometimes the altitude wiring goes from your encoder to your transponder, then the transponder has an output that sends it to your ADS-B UAT. In this case it might fail if the transponder fails.
It might be useful to know that the ADS-B transmitter must broadcast your current transponder code (1200 for vfr). The UAT generally senses it automatically as the transponder broasdcasts it so you don't need to set it in 2 different controls. But if your transponder fails, it won't sense the code and may go into a fail mode on it's own (not sure about this though).
The advent of ADS-B brings no relaxing of the regulations regarding the requirement of using transponders.


text:
Why are there some airports not charted as service-available when FBO provides fuel?
On FAA's Aeronautical Chart User's Guide - VFR Charts.

It says the tick-mark charted airports provide fuel service. However, at Airport KSIY and 1O5,

There are FBOs at both airports. e.g at Airport 1O5

Is there any reason why these service-available airports not charted as ticked. Do they need to satisfy any FAA requirements before charted?


text:
How may I verify WAAS channel number on G1000?
Take RNAV (GPS) Y RWY 36L and RNAV (GPS) Z RWY 36L at APC for examples,

All fixes and routes in the two approaches are similar.
The noticeable differences that I observe are minimums and WAAS CH number.
So some questions:
(1) How may I know which approach I am able to shoot? (or which WAAS channel is available?)
(2) Is the WAAS channel number automatically selected when I load the corresponding flight plan in G1000?
(3) ILS vs LPV: For an ILS approach, I may tune the localizer frequency and get both horizontal(CDI) and vertical (Glide Slope) information, without loading the flight plan. Can I get something similar with an LPV? I mean to get the LPV glide path guidance without loading any particular approach (set the WAAS CH number for instance?).

The WAAS channel number is unique to the approach plate. Just as the name of the approach is unique to that approach, so is the channel number. It does not refer to a radio channel or freq. Some databases allow you to look up an approach by airport -> type of approch -> runway -> etc..., some other databases allow you to type the approach channel number into the FMS to pull up the approach plate.
See AIM 1-1-19 (d) (6) for a more complete description.

One of the primary differences between the two approaches you reference is the required climb gradient. The Z approach requires a higher level of aircraft climb performance. See this sentence from the notes section: "Missed approach requires minimum climb of 480 feet per NM to 2200. If unable to meet climb gradient see RNAV (GPS) Y RWY 36L."

I found the WAAS channel number is verifiable and selectable from both PFD and MFD while in the select flight plan box. Meanwhile, the WAAS id is verifiable but not selectable.

I don't know if you can check or set the WAAS channel number directly (and I couldn't find anything about it in the C172 G1000 manual) but even if you can there's really no point. When you load the approach, the G1000 gets the WAAS channel number from the database as part of the general approach definition and configures everything automatically.
I heard or read somewhere that the original concept was that pilots would 'tune' the WAAS channel in the same way that they tune an ILS frequency, but that idea was dropped because an RNAV approach is totally dependent on the database anyway: if you trust the G1000 to load all the waypoints, altitudes and other information correctly from the database then there's no reason to think it will load the wrong WAAS channel.
As for your specific questions:
(1) How may I know which approach I am able to shoot?
You read your G1000 manual, check the approach database, and review the approach plates to make sure that the approach is available and you meet all the requirements. If the approach is in the database that doesn't automatically mean that you can fly it, there can also be climb performance or altimeter setting requirements (for example) that are unrelated to the G1000.
(2) Is the WAAS channel number automatically selected when I load the corresponding flight plan in G1000?
Yes. The G1000 sets up the approach completely for you, the only input required (usually!) is to load the approach and select how you initiate it, i.e. via an IAF or radar vectors.
(3) [Can I] get the LPV glide path guidance without loading any particular approach (set the WAAS CH number for instance?)?
No, this wouldn't make any sense. The LPV glideslope is constructed virtually by the G1000 for each approach and the WAAS input just provides correction to an existing GPS position, it doesn't give you a position directly. So even if you could receive the WAAS corrections directly (and maybe you can, for all I know), the G1000 wouldn't be able to generate a glideslope without all the other approach information about the runway, elevation etc. It would be like asking, "the magnetic declination here is 4°W, what's the correct magnetic heading to fly from A to B?" Unless you know the uncorrected heading, the correction by itself isn't useful.

for (3), I am comparing ILS and LPV, in this case. Do you think we may deploy an ILS system for an aircraft carrier, but there is no way to develop an LPV procedure for the  aircraft carrier?

@spacepure I have no idea, that could be a good question. We already have a question about autolanding on carriers, some of the links might give you some information but it isn't about ILS or LPV specifically.

The channel number does not mean what you think. The channel is a legacy of how the LPV is encoded in the nav database. The format used is the same as a GBAS approach where a local VHF transmitter was used to broadcast local diff GPS corrections for precision GPS approaches. The avionic used to fly these approaches had a code selection window where you entered a channel number - the channel number being generated based in the VHF number. When LPV came along they used the same format in the nav database as the GBAS approach but still needed a "channel" number even though there was no longer an associated VHF transmitter. ICAO manages allocation of these codes (used to be the FAA). So basically they are helpful to identify you have the correct approach but otherwise mean absolutely nothing.


text:
What are the regulations for non-aircraft targets in airport movement area?
In the movement area at a controlled airport, I would assume any airworthy aircraft is automatically eligible to make requests to enter into, exit from, transit through movement areas, for the purpose of aviation related activity.
What about the other ground vehicles and pedestrians? Do they need some  special permit, or can simply make requests like a crew member?

Related: FAA Guide to Ground Vehicle Operations For towered airports: "As an operator of a vehicle, you must have authorization from ATC before you enter any part of the airport movement area. When the tower is in operation, you must utilize a two-way radio for communicating with and receiving instructions from air traffic control."

Related: Oakland airport Air operation area (AOA) pedestrian and ground vehicle rules: "Vehicle  operators  shall  not  enter the movement area - Without  first  obtaining  permission   from  Airport  Operations  and  clearance  to  enter
the movement area  from  the ATCT; Unless  equipped  with  an  operable  two-way  radio  in  communication with the ATCT; [...]"

Ground vehicles are really problematic at an airport. The problem is not so much a matter of regulation as a problem that the people driving the vehicles sometimes are unfamiliar with flight processes so they create hazards without really understanding the danger they are creating. The "regulations" are that nobody is supposed to be on taxiways or runways without approval whatever that means, but since the FAA cannot revoke the license of somebody that does not have a license, it's a toothless rule. Also, the typical runway intruder does not even have a radio, so getting approval is problematic for them. Cops are the worst offenders. I have seen some very dangerous situations evolve from ignorant cops with no idea what they are doing just driving onto runways acting like they are god or something.
The main way the FAA interfaces to the ground control problem is to publish a lot of safety guidelines hoping that somebody will read them. Some airports have elaborate safety training for ground personnel, but the main risks usually come from untrained personnel at smaller airports where there is little or no training.
This is one of the main reasons why most airports work hard to get good fencing set up, so some bozo does not drive onto the runway.
In general, ground control takes care of authorizing vehicle movement and utility trucks are supposed to coordinate their actions with ground control. In untowered airports, utility trucks are supposed to call on CTAF to notify nearby pilots what they are doing, but unfortunately most do not have radios. Once I was landing and there was some truck on the side of the runway because the guy was removing a turtle or something. The truck had flashing lights so it was easy to see luckily.

Your cop anedocte remembered me of this old picture

That's a keeper.


text:
In G1000, how can I intercept a victor airway with multiple legs?
Suppose we are in HDG mode.
Trivially, we may visually judge which leg we on the victor airway and activate that leg.
However, in real-world, I found sometimes the fixes are so close and the airplane is relatively far from the airways. It is difficult to tell exactly which leg I am going to intercept, without "ruler" assistance. Meanwhile, ATC may change HDG assignments, and therefore the intercepted leg may change.
Is there a way to "activate the nearest leg and intercept" in G1000? or how would you solve this problem other ways?

Why not maintain HDG mode until intercepting the airway?

In G1000, the airway is segmented by fixes and we are intercepting a leg instead of the airway.

Are you in command of the aircraft or is the G1000?

Ultimately, it is me who commands the airplane, but my question is it possible to program my intention in advance and ensure the FMS matches the airplane's state throughout the whole process.

If the airway is too far away to accurately determine which leg you are going to intercept, why would you let the G1000 pick the leg you are going to intercept?
You know best what you want and, as you say, ATC may change your heading anyway.
So you shouldn't intercept automatically until you are fairly sure where you are intercepting. Instead you remain in HDG mode which gives you full control and makes it easy when ATC instructs you to change heading. Then when you are a couple of miles from intercepting you select the leg and let the G1000 do the magic if you want to.
Automation is there to relieve you from difficult or boring tasks. If you find that you spend a lot of time programming your FMS, it may be better to reduce the level of automation and spend the extra time on situational awareness.
I recommend watching this America Airlines training video on automation dependency (a.k.a. "Children of the magenta line"). It addresses the FMS / autoflight dependecies for airline pilots. The video is over 15 years old and by now similar automation systems have entered the cockpits of small aircraft. Although some aspects of the video address a multicrew environment, the main points are equally valid for G1000 equipped single crew / single engine propeller aircraft.


text:
Do I have a good CFI?
I'm studying for my PPL and I've accumulated roughly 70 hours towards my PPL and am only now doing my cross country training.  Sometimes life gets in the way.
I am a fan of my CFI but had a situation this past weekend that has made me a bit uncomfortable - he fell asleep on 3 occasions during my first cross-country.  Is this a sign of a bad CFI?  Is it something to be concerned about?
I'm also wondering - is it important to know what you're going to be expected to work on before each lesson and we figure out what we're doing for the lesson during preflight?  Right now most of the agenda is being driven by me and I'm wondering if that's normal.
What's a good/bad CFI?

General question about judging a CFI

Your CFI is PIC and should not be falling asleep... I had a great instructor, it took me 18 months to get my PPL but I did it in 45 hours. Lessons were known in advance of what we were going to practice and after every lesson was a review of what we did and what I need to work on. If you aren't happy with your CFI, its not a horrible thing to change. Remember, its your money and your time, you should get what you pay for.

One could argue that if the CFI falls asleep on your training flight then he probably had a lot of confidence in you

I'm curious about what you mean by "the agenda is being driven by me". I mean, a few flights to practice things you're not comfortable with is good, but if it has been like that from the beginning there could be an issue...

Thanks.  This is all really valuable.  I guess what I mean by the agenda is driven by me....I don't actually know what the goals of my lessons are until I'm into my preflight.  So if I'm doing cross-countries I don't have a chance to study traffic patterns of uncontrolled airports that we're flying into - in advance.

are you flying in the US? you should be briefing every flight beforehand, and if its a XC, you should be told which one of the possible airports you might go into well in advance, and you should have time to check the weather and NOTAMs. otherwise, why bother?

After reading the comments and the answers, I wondered if more information could help: Yes, it sounds like you have at a minimum an unprofessional CFI (he should be using a syllabus regardless if part 61 or 135, etc.), but if he fell asleep, he may have health issues: What altitude were you flying at when he fell asleep (>10K)? Did you have the cabin heater on? Perhaps he was experiencing some mild hypoxia or carbon monoxide poisoning. (Of course, part of your training is to recognize symptoms and take appropriate action). It might be worth a thought before abandoning him completely.

Before I comment I have to ask your training habit: Do you fly one lesson each week, or only occasional lessons because you're so busy, or 3 flying days each week, or full time?

Sometimes life gets in the way

In terms of progress, 70 hours and just starting cross country flights seems to be on the slow side. But then, if you're not training regularly, you can't blame the CFI for spending some time reviewing previous materials during each lesson.
Ideally, the flight lesson pre-flight should go like this:

CFI: Today we will be practicing steep turns. We will takeoff, head North to this area on the chart and practice there. Then we will fly North East and proceed to this airfield to practice some touch and go. Our weather report says there is weather system South of us, we need to keep an eye on it in case it moves North. I will work on the radios and navigate, you will be doing all the flying. Questions?

This establishes clear goals of the lesson. A good lesson should also conclude with a post-flight debriefing:

CFI: Today I noticed that you did not enter the traffic pattern correctly. You entered like this, which is not good because of that, that, and that. Given the situation, you should have went like this. We will be practicing more traffic patterns in our next lesson.

If the agenda is driven by the instructor instead, you'll get more benefits:

The goals of the lessons are clear.
The instructor can adjust lessons based on your weakness. For example, if you were rather sluggish during engine-out emergencies, the CFI should review emergency procedures with you on the ground and give you more practice in the air.
You may not be aware that you are not getting enough practice in some areas.
You can prepare for the next lesson ahead. For example, if your next lesson is a cross country, you can review flight planning, navigation principles & airspace regulations.

Is your situation normal? I'm not an instructor so I don't know, but it can be better. Then again, if your flying schedule is rather random, learning efficiency would be lower, and you end up spending more flying time and money.

Now, falling asleep......To me, this is a big No No. I am just a student. I have not been certified (yet) that I can operate an airplane safely:

What if I make a navigation error and end up heading to Area 51?
What if I'm heading into IMC and need to turn around?
What if the fuel level is reducing at a dangerous rate but I didn't notice?
What if I got a stuck elevator?

A flight instructor is seated in the same cockpit with the student to correct mistakes or react to situations in a timely manner. To fall asleep during a flight lesson is an irresponsible behavior to the student and other people on the ground who might get hurt if your plane crashes.
Of course, flight instructors are all humans and we all tend to make mistakes. Perhaps he was overstretching himself. Perhaps he got a family emergency the night before and stayed up really late. If it was just one flight, I would pass but keep an eye on. If it happens continuously, it might be a good time to turn away and look somewhere else while you're still safe.

I train twice a week (Sat & Sun).  I guess my feeling is that when I'm done with a session I should know what I need to study before I arrive at my next session.  But perhaps not...

Twice a week is regular training. With a bit of work & a good instructor you should get your license in only 40~50 hours. 70 hours, twice a week, just beginning cross country? I wonder how many items on the syllabus are yet to be covered. Do you feel he's teaching you new things every time you fly? Or is he just acting as a (sleepy) safety pilot? He's billed hourly, and the longer you take to get a license, the more money he'll get from you.

I'm a CFI/MEI.  I have 700-800 hours teaching private pilot students in the part 61 environment.  That's not an awesome amount but I think it's enough to comment on this question.
This guy is wildly unprofessional, maybe even criminally negligent.  You are paying him to observe you, to provide feedback, and to keep you safe.  He can do none of those things while he is sleeping on the job.
You have a lazy instructor and I'm curious to know in what other ways he is failing to teach you.
It's his job to excercise good judgement and scrub a flight if he's not up for it.  If he's overworked he shouldn't be flying.  That's his problem, not yours.  He has no excuse for his behavior and he's setting a terrible example for you to follow.  DO NOT be like your instructor.  I hope you're not using him as a role model for what a good pilot should be.
He's failing to demonstrate sound judgement and showing you that complacency is OK.
He's not challenging you or looking for teachable moments.
He's exhibiting classic hazardous attitudes...invulnerability and anti-authourity at a minimum.
I'd talk to him first and then fire him if this nonsense continues.  I'd also demand a refund on CFI billing for his nap time.
And, yes, there should be a defined lesson plan with expectations for each lesson.  This goes for pt61 and pt141 schools.  Every CFI should have created plans during their CFI training.  I have no idea how a CFI applicant can pass a CFI practical or oral exam without a comprehensive collection of lesson plans.
No, it's not OK for you to be in charge of what is covered.  You should know what the next lesson will cover so you can prepare.  He needs to give you the training plan and he needs to drive it.  Again, it's his job, it's why you pay him.
I think this guy is milking you for billable hours.  You might just be a cash pinata for him.  Either that or he's just incompetent.

I agree with what you say (I even voted you up), and I very much understand that this is a passionate subject for you (frankly, I'm similarly concerned).  But I would ask that you try and be a bit more professional in your criticisms.  While your points are entirely valid, some of the language you are using is a tad inflammatory.

That was my intent.  The original poster must be told in no uncertain terms that his instructor is failing him.  This behavior needs to be corrected quickly and decisively.  There is no excusue this CFI can give that makes sleeping on the job OK.

It's your answer and you can leave it as you wish.  But you can unequivocally state that something must be done and also be professional, for the sake of the site I wish you'd do that.  But again, the answer is yours, do as you wish.

There are few things whith which I have a no-tolerance approach.  Taking a flight when you're too tired to fly and then taking a nap while your PPL student flies because you need the $150 is beyond stupid, is dangerous, and is exactly what a CFI should not do.  The op asked if he has a bad instructor.  The answer is an objective "yes."

I already said I agree with your points, and I do believe you can word that strongly while still being professional.  Perhaps you should come find me in chat and I can explain what I mean.


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Why was the Bell Boeing V-22 Osprey not worked on more?

I've recently learned of the Bell Boeing V-22 Osprey and it appears to be a very advanced and useful vehicle. I can instantly think of reasons why the Osprey would be successful such as:
1) It can take off in small places and land in small places unlike planes
2) It can hover
3) It can turn into a plane and fly fast
4) It can pick up things like cars without the need to carry it inside like planes
5) It can easily fly sideways and backwards
So my questions are:
1) Why hasn't the Osprey advanced/been successful. For example how the F-15 went to the F-16 then the F-35 etc.
2) What made Boeing choose to have rotors instead of the faster jet engine?
The only possible reasons I can think of are things such as:
1) Stealth/noise, the Osprey requires large rotors and probably makes double the noise as a helicopter or plane would make
2) Maintenance costs, a helicopter requires more maintenance than a plane, I'd think the Osprey requires more maintenance than a helicopter or plane
3) Cost, the Osprey probably costs more than an average plane or helicopter
Though I'm not sure of the real main reason as surely those reasons can be fixed.

This question is somewhat broad and your questions seem to be based on misunderstandings. It's difficult to see where to start with an answer.

Whose to say it hasn't been successful? It has had a number of crashes, but it's in fairly widespread use, as far as I know. As far as why it hasn't been replaced, it's a relatively new aircraft. Most of them were delivered in the 2000s. Compare with the B-52s that were delivered in the 60s and are still flying or the F-15s that were delivered in the 70s and are still flying.

Can you explain in what way "the F-15 went to the F-16 then the F-35 etc."?

@JulianHzg The F-15 was worked on and it became the F-16. The F-(number) are just different versions of the same plane. Of course the F-35 is intended to be more advanced than the older F-15.

The F-16 is not a development from the F-15. The F-15 was developed by McDonnell Douglas while the F-16 was developed by competitor General Dynamics, with a lot of overlap in the timelines.

"The F-(number) are just different versions of the same plane." No they're not. Not even slightly. The "F" just means "fighter". If you look at the F-15 and F-16 on Wikipedia, you'll see that they're completely different planes, completely unrelated to each other. The F-15 is a two-engined air superiority fighter built by McDonnell Douglas (now part of Boeing); the F-16 is a significantly smaller, single-engined multi-role fighter built by General Dynamics (now part of Lockheed Martin).

@DavidRicherby Sorry for the mistake, I always though that the F-15 and F-16's were planes that were advancements of the old versions.

And F-117A isn't even a fighter ;)

Why was the Bell Boeing V-22 Osprey not worked on more?
The Osprey idea is an old one and it never worked well. For example, I have found a patent form 1921 (see the picture) for a flying machine that has some common points with the Osprey. Large diameter propellers are not efficient for planes and small rotors are not suitable for helicopters. A hybrid, like Osprey, has the advantage of not needing a runway to land or take off but at the same time, once in the air, it has to pay the price of using two inefficient propellers for flying hundreds of kilometers. Also, if it is used more as a helicopter the rotors are not as efficient as the ones of a true helicopter.

Flying machine, authour Traian Vuia, April 1921.

Bell Boeing V-22 Osprey

The Osprey has arguably been quite successful considering the circumstances. As Energizer777 points out, the basic idea is not new, and there were many engineering challenges to create a viable aircraft. That these challenges were solved and the plane is now in production and active service seems to be a pretty big success. Also, this has all happened relatively recently. The V-22 first flew in 1989 while the F-15 and F-16 both date back to the early 1970's (and are still in active service). The challenges in refining the design pushed introduction of the V-22 out until 2007. The design just hasn't had enough time to mature past the first successful application. You might consider the civilian tilt-rotor AW609, currently targeted for certification in 2017, as the next advancement of the design.
Props/rotors are more efficient than a jet engine at low speeds. Given that the slow and vertical portions of the flight are very important to the design, this decision makes sense. The prop wash also flows over the wing, allowing the wing to be more effective with a short span. Using turboshaft engines rather than jets also allows one engine to drive both rotors if the other engine fails, making single engine operation easier.
You are right about the drawbacks of the design. The V-22 is noisy and not as agile has a helicopter in slow flight. Maintenance requirements are high and were certainly an issue early on in the introduction to service. And upfront costs are also more than a helicopter or airplane of comparable size. However, the capabilities you listed first are worth these added costs, at least to those that have purchased/ordered the V-22.

I'd argue that it's been quite successful.  Think various comments have cleared that up, as well as modifying your definition of "successful."
A necessary forerunner to it was the XV-15.  Yes, there were earlier aircraft, but this didn't work well until smaller turboprop engines, with sufficient power density became available.  Prior to that, the engines were usually located in the fuselage and had driveshafts carrying the power to the nacelles on the wingtips.  These were heavy and prone to failure.
As for why the Osprey has props/rotors instead of jets, let's talk about thrust and power.  To get off the ground, you need more thrust than you have weight.  Typically, if you're going to do VTOL, you need 110% as much.  So a 2,000 pound aircraft needs at least 2,200 pounds of thrust to takeoff vertically, much less hover.  Hover requires even more.
There are multiple ways to make thrust:

grab a relatively small amount of air mass and accelerate the heck out of it.  This is what turbojets and afterburning low-bypass turbofans do, as found in most fighter planes.  There will be high-speed jet efflux, high temperatures and comparatively high fuel consumption with this route.  The Harrier does this, as does the F-35B.  Neither can do it for very long, though (significant fuel consumption), and you don't want to be anywhere nearby, on the ground, when they do it (noisy, windy, hot).  If you need to go FAST, you need to do this.
grab a relatively large amount of air mass and accelerate it a little bit.  This is what the rotor does on a helicopter and, to a lesser degree, a propeller on an airplane.  The rotor/prop wash has nowhere near the intensity of a jet engine's exhaust.  There's also less heat and much less fuel consumption.  But you can't go as fast (speed is limited by the airspeed of the rotor/prop wash).
somewhere in between.  High bypass turbofans on modern jetliners grab more air than turbojets, but less than props/rotors, and they accelerate the air more than a prop/rotor but less than a turbojet.  Lower fuel consumption than the turbojet and less noise but higher speed than a prop/rotor.

If they could've done it with a single rotor, and found a way to angle that forward for "airplane" mode, they'd have done so; a single, large rotor would be more efficient than a pair of smaller rotors.  The simplest mechanism they could develop, which would provide the capabilities of both airplane and helicopter, was a twin-engine design.  You get a faster cruise speed and a longer range than any helicopter in the inventory and a broader flight envelope than any airplane (VTOL and hover).
Additionally, you need a degree of agility for maneuvering in hover.  So you need the ability to change the thrust vectors while hovering; the "airplane" flight controls (ailerons, elevators and rudder) are useless in this mode.  To accomplish this, the props/rotors have collective and cyclic controls like a helicopter.  If you flatten the pitch on the forward part of the rotation, that will change the thrust vector to push down-and-aft, instead of just down.  Coordinate this between the two engines and you have translation forward/aft, side-to-side and pivot, just like a helicopter.
To my knowledge, no one has succeeded in making a jet engine which can do this.
A jet-engined variant would likely need some kind of 2D thrust vectoring, downstream of the actual engine.  There are existing examples of this:

The F-22 does 1D thrust vectoring (each engine nozzle can pitch up/down).  Used differentially, this can augment pitch AND roll.
The Su-35 does something similar to the F-22
The F-35B, as mentioned, does limited 1D thrust vectoring for STOVL
Some advanced Mig-29s do full 2D thrust vectoring with both nozzles
The F-16 VISTA demonstrator did full 2D thrust vectoring
The X-31 also had basic 2D thrust vectoring, due to some deflector "paddles" aft of the engine.  This is similar to the directional vanes used on the original V-2 rocket.

Assuming someone can come up with a usable 2D thrust vectoring system, mounted to the aft end of high-bypass turbofan (all the mentioned examples are turbojets, lower-bypass turbofans or rockets), it might be possible to do a jet-powered variant, at some point in the future.

Well reasoned, however, I take umbrage with your thrust vectoring comments. I would say that thrust vectoring is NOT still quite experimental. We have several discussion here, here, and notably on 2 line-use fighters here.

Excellent feedback @FreeMan.  I've modified the section about the thrust vectoring, including some links.

The F-35B... does limited 1D thrust vectoring. The F-35B actually has "3D" TVC in hover mode. The rear nozzle can wiggle forward/aft/left/right, the roll posts provide roll control, and the lift fan's thrust can also be vectored somewhat. In a hover, the F-35B can basically translate forward/back/left/right and turn in place. (Oh, sorry, I thought this was posted today, not last year.)

It doesn't need to be updated
It already does everything the Marines need it to do. Replacing it would be expensive for no reason.
The other aircraft you mention, F-15, F-16, F-35, F-22 are a little different - the F-35 is replacing the F-18/F-16. The F-18 replaced the F-14. The F-22 is mostly a replacement for the F-15. Why? Because these get outdated.
The USAF's potential enemies build a fighter that can beat the F-15, so you build a fighter that can beat their new one. Repeat. This has happened since the dawn of the fighter aircraft.
Transport aircraft, however... what would you improve? It's already about as fast as it's going to get without a lot of money being spent, and as capable.
Quite simply, there's no need to replace it yet. That doesn't mean it's been unsuccessful.

To add, the MV-22B is mostly a replacement for helos (namely the CH-46E and CH-53E), to which the MV-22B is generally superior: greater combat radius, almost doubled cruise speed / shorter transit time, good payload, and much higher cruise altitude, putting it above most MANPADS and AAA. Consequently, the V-22 can get things done faster and with less risk, being less vulnerable for less time each mission.


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How to fly to an uncharted airport?
I'm learning X-Plane 11 and started to use an add-on called FS Economy.
One of its missions is to fly to small airports that I can't find on skyvector, so I'm unable to plan a direct flight.
I usually fly to the nearest charted airport, and fly using the GPS from there. Not knowing any information like runway length beforehand.
How realistic is it in the real world that an airport would not be charted, and how are flights planned to such airport?

For farm/private strips in the UK we usually just telephone the landowner and ask him to move his harvester/classic car collection/hay bails and ask for any details we need.

They  are  planned pretty much as you do, navigate to somewhere close that is charted like an aerodrome, VOR or other nav fix, then dead reckoning or GPS from there.

Pilotage - you look out the window

As a frequent flyer to uncharted airports, I simply use a VOR radial and distance when filing.  Usually the approach controllers are familiar with local airports, even infrequent use ones.  When in an area where there is no approach facility the center controller may be less familiar with the airport. I normally provide the owner's phone as a destination contact.
While one could use a lat/long coordinate, a radial and dme is easier to communicate.
Depending upon what I am doing, sometimes 20% of my landings are at uncharted airports. One can file VFR and IFR flight plans to them.
This doesn't specifically address your use of X-plane 11, but it is intended to describe operations in general aviation in North America, and my less limited experience in South America.

I like this answer, the problem/question is not specific to X-Plane but I wanted to be clear that I am using a simulator and not a trained pilot. That said VOR and radials are easy enough.

I know nothing of X-plane, but I fly gliders in real life and often land in fields and "uncharted" airports.  Uncharted does not mean the airport does not exist. However, you do need some idea of where it is, GPS coordinates, or some fix from a known point.  Even a general description of its location can get you close enough to find it.  I have often used "Google Earth" to pinpoint a potential landing area and once I find it there, I have what I need to navigate to it.  I check the date of the GE photography some are several years old and things could have changed that make the field unsuitable.
GE also has tools that you can use to measure the length and width of the "runway" and its orientation.  I look for obstacles that might interfere with my approach.  I also check to see if it is fenced because that can complicate getting my glider out of the field.

If it's not known to the FAA, it's not going to be available in a standard navigational database.  You would have to know of the existence of the airstrip beforehand and get the lat-long coordinates for it.  If you have those, you can create custom waypoints in a GNSS unit e.g. GNS430, GTN750, etc. to fly to.  This can also be done in the air if you locate an airstrip and note the lat-long coordinate or a polar bearing/distance from a know nav beacon like a VOR or NDB, which also can be used to create GPS waypoints as well.

The FAA maintains a list of uncharted airports.  An airport need not be on their list, but just because it is uncharted doesn't mean that there is not an entry in a database for it.


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How many minutes between jetway (air bridge) detachment and take-off?
Is there a standard policy / guideline that dictates how many minutes a jetway or air bridge must be detached from a commercial aircraft before take-off?

I'm not aware of any actual regulatory minimum and can't imagine why any would make sense. It's usually just a matter of how ever long it takes to do all of the stuff that must be done between those two events (e.g. secure doors, wait for permission to pushback, actually pushback, start engines, run various pre-flight checklists, taxi to runway, wait in line for takeoff clearance, etc.)

@reirab your answer makes sense to me -- and while I don't think such a regulatory minimum would make sense, I'm still curious about whether it exists.

While removing the jetway is a decision (albeit execution is also depending on external factors), take-off is subject to uncertainties (preceding aircraft, landing aircraft). So knowing when it's time to remove the jetway to meet a delay before take-off seems impossible in general.

@ReefLoretto, I'm curious as to why you asked this question, is it part of a wider problem you are trying to solve?

@GdD -- I wish it were something more important than this, but I recently had an encounter where someone made a big scene about how they arrived at their gate prior to scheduled take-off, but were not allowed to board because the jetway had been detached. They claimed that this was "entirely out of regulation."

The vast majority of people have no idea what regulations are, so they were probably talking complete garbage out of frustration @ReefLoretto

while I don't think such a regulatory minimum would make sense, I'm still curious about whether it exists.

No, there is no such regulatory minimum.
On average, it's between 10 and 20 minutes from pushback to takeoff, although there are a couple of places I can think of (very short taxi from gate to runway) that I've seen it done in under five minutes.  That's moving pretty fast, though -- almost nonstop checklists, other than during the time the engines are starting.  But whatever you can do safely, is fine as far as regulations are concerned.  If you're ready to go, no regulation makes you wait.
Depending on the aircraft, there may be an engine warmup requirement or recommendation.  That's typically much more restrictive for the first flight of the day, and that would be a limiting factor in the very short taxi cases.


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How is thrust of engines on the two sides of an airplane kept exactly equal to prevent yawing?
I assume that the thrust of engines on the two sides must be kept exactly equal otherwise the plane would start yawing. What mechanism is used to prevent this from happening?

Rudder trim? I'm speculating. I could be wrong.

Are you asking how to equalize the thrust of the engines, or how to counteract the resulting yaw?  Both seem like interesting questions, but the question title asks the former while the body asks the latter.

Yaw will occur for other reasons than asymmetrical thrust, so equal thrust is not so critical. Such reasons include icing and cross-wind.

@mins Cross wind during cruise is no factor on yaw, only during takeoff and landing

Thought experiment: you're flying along at cruse in a twin-engine airliner when one of the engines suddenly fails. The thrust on each side is now very much asymmetric, yet the aircraft does not spiral out of control. Clearly, if this abnormal situation can be handled with relative ease, the thrust doesn't need to be kept exactly equal in normal operations.

I have to disagree. When you have a cross wind while not aligning the aircraft with a runway (nearly always except for takeoff and landing), you are basically flying straight through the 'airmass', but sideways over the ground. As long as you are flying straight through the air there should be no force required from the rudder unless it is to compensate for asymmetrical thrust

https://en.m.wikipedia.org/wiki/Crosswind_landing

At first the aircraft flies straight into the wind without the use of rudder (side slip approach). Then, just before touchdown the pilot (many aircraft) will attempt to align the aircraft with the runway using rudder and compensating with roll to prevent being blown away from the runway (cross-controlled landing)

Heading is where you point your nose, (ground)track is where you are actually going with reference to the earth. So if there is no wind and you head north, track and heading are the same. If you have wind from the west with a heading of north, your track will be a few degrees more to the east. If you want your track to be north, you must alter your heading to be somewhat more westerly. You do that by turning the aircraft (by rolling) to have the correct heading for the intended track. You are then still flying straight through the air-mass

@mins I don't think we are in agreement. It make  no difference to the plane cruising through an air mass that is stationary or a moving air mass. Only the track will be different. If you compensate for cross wind in the cruise, you should still have the slip-ball in the middle and there is no force needed from the rudder to counteract for cross wind. I took a picture today of my EFIS display, but cannot add it to a comment

@mins Here is a link (http://pasteboard.co/16BvDO4g.jpg) to a picture I pasted. Don't know how long it will be available. You can clearly see the difference between heading (yellow pointer at the top of the arc) and the track (brown diamond shape). If you look to the left screen, you can see that the slip-rectangle is in the middle...well, as well as the autopilot was able to get it in the middle. Hope this clarifies it a bit

It isn't. The rudder is used.
Yes, if there is asymmetry in thrust, the plane will yaw. And there is asymmetry in thrust. The engine thrust decreases slightly with wear and the engines are often worn out differently. There are effects like P-factor that shift the thrust axis depending on speed and attitude. And of course an engine may fail.
So thrust asymmetry happens and needs to be compensated. And it is compensated by generating some sideways force with the rudder. Either by pilot pushing the pedal, or by applying trim.
As @mins mentions, there are also effects that can cause asymmetry of drag, e.g. icing, and there are situations where the aircraft intentionally needs to fly somewhat sideways, e.g. cross-wind take-off and landing, so rudder is needed for many other things too. And when it's there, it can compensate thrust asymmetry (often, though, the engine failure dictates the minimum size of the vertical stabilizer and rudder).
Note, that P-factor occurs in single-engine propeller aircraft too, so they also have some thrust asymmetry.

Don't know if this might be worth a different question, but wouldn't it be more efficient to be able to balance the thrust of the engines exactly, like with some kind of 'throttle trim'? Of course that would not work with an inoperative engine, but it could compensate for the small, wear related differences Jan Hudec mentioned. IMO deflecting rudder continuously means a lot of drag that could be avoided this way.

@RobVermeulen, there is no exactly in the physical world! You can only match the thrust as well as you can measure it and measuring thrust precisely is rather hard. Deflecting the rudder a little bit adds only a little bit of drag and the differences are small enough as they are that it's not worth a complicated device.

"the engines are often worn out differently" - a very good point. Most airliners will be flying with two(+) engines with very different numbers of flight hours. It's not unusual for an aircraft to have a 6,000 hour engine and a 25,000 hour engine, for example.

This is not true. It very much depends on the aircraft type. The B737 (NG) and B767 use both the rudder and thrust management to counter asymmetric thrust. The B787 does not use the rudder for this at all.

@Jan Hudec, I understand from your comment that measuring thrust exactly at the source isn't trivial. But is isn't necessary either. The input of such a feedback loop could be the resulting asymmetry as it results in yaw. Which is readily detectable: it is the same input the pilot now uses to apply the right amount of rudder trim. But well, this is merely theorizing, as I understand the amount of yaw/trim/drag is not worthwhile. And the 'complicated device' is already in place and paid for: the pilot.

Would the FADEC/EEC play a role for equipped aircraft? They may adjust engine parameters so that the commanded thrust is actually obtained, regardless of the engine condition (to some extent).

@mins, it's less matter of FADEC and more a matter of how accurately the parameters can be measured and how well they reflect the actual thrust. AFAIK there is no parameter that would be directly related to thrust.

This depends on the airframe and where the engines are mounted. The father inboard the engines the less of an issue a slight variation in thrust will cause. But as mentioned the rudder is the general correction for this yaw.
The closest thing I can think of (and its not really for thrust balance although that is a byproduct of its function) is a Synchronizer/Synchronizer which can be found on some multi engine propeller planes. These devices are mainly to prevent harmonic beats from becoming irritating to the occupants to do so they keep the propellors spinning at near identical RPM's. If you engines are in tune and generating about the same power you should get near identical thrust from them.
The MD80 did have an engine sync system that was able to match RPM's of the N1 or N2 stages of the jets. It seems that this may have been mainly for noise but symmetrical thrust would also have been a byproduct more or less.
Here is an interesting patent on engine sync systems

Actually, for a propeller engine with constant-speed propeller the thrust and rpm are completely independent variables (or almost; rpm limits power, but high rpm with low power is perfectly normal and used during approach). So you still rely on the same power, and the same power is hard.